Method for coating metallic surfaces with an aqueous composition

ABSTRACT

A process for coating a metallic surface by contacting the metallic surface with a first coating composition to form a first coating on the metallic surface, wherein the first coating composition contains water and at least one compound a) selected from a silane, a silanol, a siloxane and a polysiloxane. The first coating is the rinsed with an aqueous surfactant-containing fluid without drying so that the at least one compound a) does not condense before the rinsing step. The silane, silanol, siloxane or polysiloxane is capable of condensation.

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/985,652 filed Nov. 10, 2004, and is a §371 ofPCT/EP2005/011953 filed Nov. 9, 2005. This application also claimspriority from German Patent Application No. 10 2005 015 573.1 filed Apr.4, 2005, German Patent Application No. 10 2005 015 576.6 filed Apr. 4,2005 and German Patent Application No. 10 2005 015 575.8 filed Apr. 4,2005.

The invention relates to a process for coating metallic surfaces with anaqueous composition containing at least one silane and/or relatedsilicon-containing compound and optionally other components, which istreated further, e.g. at temperatures above 70° C., without drying thecoating.

The processes most commonly employed hitherto for the treatment ofmetallic surfaces, especially parts, coil or coil portions made of atleast one metallic material, or for the pretreatment of metallicsurfaces prior to lacquering are frequently based on the one hand on theuse of chromium (VI) compounds, optionally together with diverseadditives, or on the other hand on phosphates, e.g.zinc/manganese/nickel phosphates, optionally together with diverseadditives.

Because of the toxicological and ecological risks associated especiallywith processes using chromate or nickel, alternatives to these processesin all the areas of surface technology for metallic substrates have beensought for many years, but it has repeatedly been found that, in manyapplications, completely chromate-free or nickel-free processes do notsatisfy 100% of the performance spectrum or do not offer the desiredsafety. Attempts are therefore being made to minimize the chromatecontents or nickel contents and to replace Cr⁶⁺ with Cr³⁺ as far aspossible. High-quality phosphatizing processes are used especially inthe automobile industry, e.g. for the pretreatment of car bodies priorto lacquering, which have maintained the quality of automobile corrosionprotection at a high level. Zinc/manganese/nickel phosphatizingprocesses are conventionally employed for this purpose. Despite manyyears of research and development, attempts to phosphatize nickel-freewithout pronounced quality limitations have proved unsuccessful formultimetal applications such as those often involved in car bodies,where, in Europe, metallic surfaces of steel, galvanized steel andaluminium or aluminium alloys are typically pretreated in the same bath.However, since nickel contents, even if comparatively small, are nowclassified as being of greater toxicological concern for the foreseeablefuture, the question arises as to whether an equivalent corrosionprotection can be achieved with other chemical processes.

The use e.g. of silanes/silanols in aqueous compositions for theproduction of siloxane/polysiloxane-rich anticorrosive coatings is knownin principle. For the sake of simplicity,silane/silanol/siloxane/polysiloxane will hereafter often be referred toonly as silane. These coatings have proved themselves, but someprocesses for coating with an aqueous composition containingpredominantly silane, in addition to solvent(s), are difficult to apply.These coatings are not always formed with outstanding properties.Moreover, adequate characterization, with the naked eye or optical aids,of the very thin, transparent silane coatings on the metallic substrate,and their defects, can be problematic. The corrosion protection and thelacquer adhesion of the siloxane- and/or polysiloxane-rich coatingsformed are often high, but not always; in some cases, even withappropriate application, they are insufficiently high for particularuses. There is a need for other processes, using at least one silane,which offer a high process safety and a high quality of the coatingsproduced, especially in respect of corrosion resistance and lacqueradhesion.

In the formulation of silane-containing aqueous compositions, it hasalso proved beneficial to add a small or large amount of at least onecomponent selected from the group comprising organic monomers, oligomersand polymers. The type and amount of silane added to such compositionsis in some cases of decisive importance for the outcome. Conventionally,however, the amounts of silane added are comparatively small—usuallyonly up to 5 wt. % of the total solids content—and they then function asa coupling agent, where the adhesion-promoting action should prevailespecially between metallic substrate and lacquer and optionally betweenpigment and organic lacquer constituents, but a slight crosslinkingaction can also occur in some cases as a secondary effect. Chiefly, verysmall amounts of silane are added to thermosetting resin systems.

The other two patent applications on a similar subject matter submittedto the same patent office on the same date are expressly included here,especially in respect of the aqueous compositions, the additions to theaqueous compositions, the steps before, during and after coating, thebath behaviour, the layer formation, the layer properties and theeffects determined, particularly in the Examples and ComparativeExamples. Likewise, the patent applications that give rise to a right ofpriority are also expressly included in the subsequent patentapplications.

It is currently known that, when using silane-containing solutions forcoating metallic surfaces, the solutions containing essentially orpredominantly silane and derivatives thereof are water-sensitive if thecoatings have not been dried more substantially, so rinsing of thefreshly applied and not yet thoroughly dried coatings with waternormally leads to impairment of the coatings, e.g. due to peeling,because they are not sufficiently rinse-resistant. Evidently the verythin oxide/hydroxide layers of the “natural” oxide skins of metallicsurfaces are not sufficient to keep freshly applied silane adequatelyadhesive prior to thorough drying. Only if the coatings are dried e.g.for 5 minutes at 80° C. PMT (peak metal temperature), for 25 minutes at70° C. PMT or more substantially are these coatings normally insensitiveto water, because the condensation of thesilanes/silanols/siloxanes/polysiloxanes is more advanced. The extent ofdrying, which is associated with condensation of thesilanes/silanols/siloxanes/polysiloxanes and makes thesiloxane/polysiloxane-containing coating rinse-resistant, variesaccording to the existence of phases, the coating and the type ofrinsing.

Existing phosphatizing units, especially in the automobile industry forthe cleaning and pretreatment of car bodies prior to lacquering, do notneed a drying unit. Even without a drying unit, however, such achannel-like unit is often well over one hundred metres long. In manycases, at the end where the newly phosphatized car bodies come out ofthe channel, these units are joined directly to a unit for coating witha cathodic dip lacquer (CDL), so normally there is no space availablefor the additional construction of a drying unit.

The object was therefore to propose aqueous compositions whose coatingshave an environmentally friendly chemical composition and assure a highcorrosion resistance, and which are also suitable in multimetalapplications in which e.g. steel and zinc-rich metallic surfaces, andoptionally also aluminium-rich metallic surfaces, are treated orpretreated in the same bath. The object was also to propose apretreatment process, especially for car bodies in automobile massproduction, which can be carried out with silane-containing solutions inthe simplest and safest possible manner. The object was also to proposea process using silane-containing aqueous compositions which inprinciple can be carried out in existing plants in the automobileindustry and is particularly suitable for coating car bodies inautomobile construction. The quality of the coatings on car bodysurfaces achieved by this process should come as close as possible tothe properties of the high-quality anticorrosive coatings produced byzinc/manganese/nickel phosphatizing processes, so as not to compromisethe quality standard.

It has now been found that the addition of at least one complex fluoridehelps to minimize or avoid impairments of the bond between the silaneand the metallic surface so that rinsing can only have a very slightimpairing effect, if any. It has now also been found that a combinationof at least two complex fluorides, especially fluorotitanic acid andfluorozirconic acid, affords an exceptional increase in quality of thecoating.

It has now been found not only that it is possible to rinse freshlyapplied silane-based coatings that have not yet dried thoroughly andhence not yet condensed more substantially, but also that this processsequence is even advantageous, because the coatings produced and rinsedin this way even have better corrosion protection and better lacqueradhesion, to some extent independently of the chemical composition ofthe aqueous bath. This contradicts earlier experiences where the rinsingof a freshly applied silane-based coating that has not yet dried moresubstantially easily and frequently leads to an impairment of thequality of the layer, or even to the removal of part or, occasionally,all of the coating.

It has now also been found that it is possible and advantageous to applya lacquer, a lacquer-like coating, a primer or an adhesive to freshlyapplied silane-based coatings that have not yet dried thoroughly andhence not yet condensed more substantially, which may also have beenrinsed in this state. The application of such compositions tosilane-based wet films is advantageous because the coatings produced andrinsed in this way even have better corrosion protection and betterlacquer adhesion, to some extent independently of the chemicalcomposition of the aqueous bath.

The object is achieved by a process for coating metallic surfaces with acomposition containing silane/silanol/siloxane/polysiloxane, thecomposition containing the following in addition to water and optionallyin addition to at least one organic solvent and/or at least onesubstance that influences the pH:

-   -   at least one compound a) selected from silanes, silanols,        siloxanes and polysiloxanes, at least one of these compounds        still being capable of condensation, and optionally also    -   at least one compound b) containing titanium, hafnium,        zirconium, aluminium and/or boron,    -   at least one type of cation c) selected from cations of metals        of subgroups 1 to 3 and 5 to 8, including lanthanides, and of        main group 2 of the periodic table of the elements, and/or at        least one corresponding compound, and/or    -   at least one organic compound d) selected from monomers,        oligomers, polymers, copolymers and block copolymers,    -   wherein the coating freshly applied with this composition is        rinsed with a fluid and is not dried thoroughly before this        rinsing step so that the at least one compound a) capable of        condensation does not condense substantially before the coating        is rinsed.

The object is also achieved by a process for coating metallic surfaceswith a composition containing silane/silanol/siloxane/polysiloxane, thecomposition containing the following in addition to water and optionallyin addition to at least one organic solvent and/or at least onesubstance that influences the pH:

-   -   at least one compound a) selected from silanes, silanols,        siloxanes and polysiloxanes, at least one of these compounds        still being capable of condensation, and optionally also    -   at least one compound b) containing titanium, hafnium,        zirconium, aluminium and/or boron,    -   at least one type of cation c) selected from cations of metals        of subgroups 1 to 3 and 5 to 8, including lanthanides, and of        main group 2 of the periodic table of the elements, and/or at        least one corresponding compound, and/or    -   at least one organic compound d) selected from monomers,        oligomers, polymers, copolymers and block copolymers,    -   wherein the coating freshly applied with this composition is not        dried thoroughly before the application of a subsequent coating        so that the at least one compound a) capable of condensation        does not condense substantially before the application of the        subsequent coating.

The content of the patent application that gives rise to a right ofpriority to the present patent application, DE 102005015576.6, thecontent of the other, related patent applications that give rise to aright of priority, DE 102005015573.1, DE 102005015575.8 and U.S. Ser.No. 10/985,652, and the content of the parallel PCT applications issuingfrom the three last-mentioned patent applications that give rise to aright of priority, is to be expressly included in the present patentapplication, especially in respect of the different compositions,different compounds added, different process steps, different coatingsproduced, Examples, Comparative Examples and effects, properties andlaboratory results mentioned therein.

The subsequent coating can be a second conversion coating, a coatingresulting from the application of an afterrinsing solution, or a coatingbased on a lacquer, a lacquer-like composition, a primer or an adhesive.

The second conversion coating or the coating resulting from theapplication of an afterrinsing solution is preferably an aqueouscomposition based on at least one silane/silanol/siloxane/polysiloxane,at least one compound containing titanium, hafnium, zirconium, aluminiumand/or boron (e.g. at least one complex fluoride), at least one organiccompound selected from monomers, oligomers, polymers, copolymers andblock copolymers, and/or at least one compound containing phosphorus andoxygen. In many embodiments the concentration of the aqueous compositionfor the second conversion coating, or of the afterrinsing solution, isoverall lower than that of a comparable aqueous composition for thefirst conversion coating, i.e. the silane pretreatment layer accordingto the invention.

It is particularly advantageous if the freshly applied coating is firstrinsed with a fluid before a subsequent coating is applied. In this casethe wet film of the silane pretreatment according to the invention canbe rinsed with water or with an aqueous composition optionallycontaining surfactant, without the wet film being dried moresubstantially beforehand. A subsequent coating can then be applied tothis wet film while it is still in an insubstantially dried state,especially by the application of a lacquer, a lacquer-like composition,a primer or an adhesive. The rinsing of the wet film after the silanepretreatment is preferably carried out immediately after coating withthe silane-containing aqueous composition, especially within one or twominutes of coating with the silane pretreatment according to theinvention, particularly preferably within 30 seconds or even within 10seconds of this coating step. The lacquer, lacquer-like composition,primer or adhesive is preferably applied immediately after rinsing,especially within two or three minutes of the rinsing of thesilane-containing coating, particularly preferably within 60 seconds oreven within 20 seconds. The lacquer in this case can be especially anelectro-dip lacquer or a wet lacquer containing water.

It is assumed that the at least one silane still capable of condensationis even more chemically-reactive, and in particular can react moreintensely with a subsequently applied primer, lacquer, lacquer-like oradhesive layer, than a silane that has already been dried thoroughly andhas condensed substantially under the influence of heat.

The word “silane” is used here for silanes, silanols, siloxanes,polysiloxanes and their reaction products or derivatives, which oftenare also “silane” mixtures. In terms of the present patent application,the word “condensation” denotes all forms of crosslinking, furthercrosslinking and further chemical reactions of thesilanes/silanols/siloxanes/polysiloxanes. In terms of the present patentapplication, the word “coating” refers to the coating formed with theaqueous composition, including the wet film, the dried-on film, thethoroughly dried film, the film dried at elevated temperature and thefilm optionally crosslinked further by heating and/or irradiation.

The aqueous composition is an aqueous solution, an aqueous dispersionand/or an emulsion. The pH of the aqueous composition is preferablygreater than 1.5 and less than 9, particularly preferably in the rangefrom 2 to 7, very particularly preferably in the range from 2.5 to 6.5and especially in the range from 3 to 6. At a pH of 2.5, for example, amarkedly reduced deposition of titanium or zirconium compounds from thecomplex fluoride can occur, causing a slight degradation of the layerproperties. At a pH of about 7, the bath containing the complex fluoridecan become unstable and precipitations can occur.

Particularly preferably, at least one silane and/or at least onecorresponding compound having at least one amino group, urea groupand/or ureido group (imino group) is added to the aqueous compositionbecause the coatings produced therewith often exhibit a greater lacqueradhesion and/or a higher affinity for the subsequent lacquer layer. Inparticular, when using at least one silane and/or at least onecorresponding compound having at least one such group, it should bepointed out that condensation may proceed very rapidly at pH valuesbelow 2. The proportion of aminosilanes, ureidosilanes and/or silaneshaving at least one urea group, and/or of corresponding silanols,siloxanes and polysiloxanes, relative to the sum of all types ofcompounds selected from silanes, silanols, siloxanes and polysiloxanes,can preferably be high, particularly preferably above 20, above 30 orabove 40 wt. %, calculated as the corresponding silanols, veryparticularly preferably above 50, above 60, above 70 or above 80 wt. %and possibly even up to 90, up to 95 or up to 100 wt. %.

Preferably, the aqueous composition has a content ofsilane/silanol/siloxane/polysiloxane a) ranging from 0.005 to 80 g/l,calculated on the basis of the corresponding silanols. This content isparticularly preferably in the range from 0.01 to 30 g/l, veryparticularly preferably in the range from 0.02 to 12 g/l, to 8 g/l or to5 g/l and especially in the range from 0.05 to 3 g/l or in the rangefrom 0.08 to 2 g/l or to 1 g/l. These ranges of contents referparticularly to bath compositions.

However, if a concentrate is used to prepare a corresponding bathcomposition, especially by dilution with water and optionally by theaddition of at least one other substance, it is advisable, for example,to keep a concentrate A containing silane/silanol/siloxane/polysiloxanea) separate from a concentrate B containing all or almost all of theremaining constituents, and only to bring these components together inthe bath. This optionally also makes it possible for at least onesilane, silanol, siloxane and/or polysiloxane to be partially orcompletely in the solid state, to be added in the solid state and/or tobe added as a dispersion or solution. However, the main emphases of thecontents in the concentration ranges of the bath can vary with theapplication.

Particularly preferably, the composition contains at least one silane,silanol, siloxane and/or polysiloxane a) having in each case at leastone group selected from acrylate groups, alkylaminoalkyl groups,alkylamino groups, amino groups, aminoalkyl groups, succinic anhydridegroups, carboxyl groups, epoxy groups, glycidoxy groups, hydroxylgroups, ureido groups (imino groups), isocyanato groups, methacrylategroups and/or urea groups.

The silanes, silanols, siloxanes and/or polysiloxanes in the aqueouscomposition, or at least their compounds added to the aqueouscomposition, or at least some of these, are preferably water-soluble. Interms of the present patent application, the silanes are regarded aswater-soluble if together they have a solubility in water of at least0.05 g/l, preferably of at least 0.1 g/l and particularly preferably ofat least 0.2 g/l or at least 0.3 g/l at room temperature in thecomposition containing silane/silanol/siloxane/polysiloxane. This doesnot mean that each individual silane must have this minimum solubility,but that these minimum values are achieved on average.

The aqueous composition preferably contains at least onesilane/silanol/siloxane/polysiloxane selected from fluorine-free silanesand the corresponding silanols/siloxanes/polysiloxanes, consistingrespectively of at least one acyloxysilane, alkoxysilane, silane havingat least one amino group, such as an aminoalkylsilane, silane having atleast one succinic acid group and/or succinic anhydride group,bis(silyl)silane, silane having at least one epoxy group, such as aglycidoxy-silane, (meth)acrylatosilane, poly(silyl)silane, ureidosilaneor vinylsilane, and/or at least one silanol and/or at least one siloxaneor polysiloxane whose chemical composition corresponds to that of thesilanes mentioned above. It contains at least one silane and/or (in eachcase) at least one monomeric, dimeric, oligomeric and/or polymericsilanol and/or (in each case) at least one monomeric, dimeric,oligomeric and/or polymeric siloxane, oligomers being understoodhereafter to include dimers and trimers. Particularly preferably, the atleast one silane or the corresponding silanol/siloxane/polysiloxane hasin each case at least one amino group, urea group and/or ureido group.

In particular, the composition contains at least one silane and/or atleast one corresponding silanol/siloxane/polysiloxane selected from thefollowing group or based thereon:

-   -   (3,4-epoxyalkyl)trialkoxysilane,    -   (3,4-epoxycycloalkyl)alkyltrialkoxysilane,    -   3-acryloxyalkyltrialkoxysilane,    -   3-glycidoxyalkyltrialkoxysilane,    -   3-methacryloxyalkyltrialkoxysilane,    -   3-(trialkoxysilyl)alkylsuccinosilane,    -   4-aminodialkylalkyltrialkoxysilane,    -   4-aminodialkylalkylalkyldialkoxysilane,    -   aminoalkylaminoalkyltrialkoxysilane,    -   aminoalkylaminoalkylalkyldialkoxysilane,    -   aminoalkyltrialkoxysilane,    -   bis(trialkoxysilylalkyl)amine,    -   bis(trialkoxysilyl)ethane,    -   gamma-acryloxyalkyltrialkoxysilane,    -   gamma-aminoalkyltrialkoxysilane,    -   gamma-methacryloxyalkyltrialkoxysilane,    -   (gamma-trialkoxysilylalkyl)dialkylenetriamine,    -   gamma-ureidoalkyltrialkoxysilane,    -   N-2-aminoalkyl-3-aminopropyltrialkoxysilane,    -   N-(3-trialkoxysilylalkyl)alkylenediamine,    -   N-alkylaminoisoalkyltrialkoxysilane,    -   N-(aminoalkyl)aminoalkylalkyldialkoxysilane,    -   N-beta-(aminoalkyl)-gamma-aminoalkyltrialkoxysilane,    -   N-(gamma-trialkoxysilylalkyl)dialkylenetriamine,    -   N-phenylaminoalkyltrialkoxysilane,    -   poly(aminoalkyl)alkyldialkoxysilane,    -   tris(3-trialkoxysilyl)alkylisocyanurate,    -   ureidoalkyltrialkoxysilane and    -   vinylacetoxysilane.

Particularly preferably, the composition contains at least one silaneand/or at least one corresponding silanol/siloxane/polysiloxane selectedfrom the following group or based thereon:

-   -   (3,4-epoxybutyl)triethoxysilane,    -   (3,4-epoxybutyl)trimethoxysilane,    -   (3,4-epoxycyclohexyl)propyltriethoxysilane,    -   (3,4-epoxycyclohexyl)propyltrimethoxysilane,    -   3-acryloxypropyltriethoxysilane,    -   3-acryloxypropyltrimethoxysilane,    -   3-aminopropylsilanetriol,    -   3-glycidoxypropyltriethoxysilane,    -   3-glycidoxypropyltrimethoxysilane,    -   3-methacryloxypropyltriethoxysilane,    -   3-methacryloxypropyltrimethoxysilane,    -   3-(triethoxysilyl)propylsuccinosilane,    -   aminoethylaminopropylmethyldiethoxysilane,    -   aminoethylaminopropylmethyldimethoxysilane,    -   aminopropyltrialkoxysilane,    -   beta-(3,4-epoxycyclohexyl)ethyltriethoxysilane,    -   beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,    -   beta-(3,4-epoxycyclohexyl)methyltriethoxysilane,    -   beta-(3,4-epoxycyclohexyl)methyltrimethoxysilane,    -   bis-1,2-(triethoxysilyl)ethane,    -   bis-1,2-(trimethoxysilyl)ethane,    -   bis(triethoxysilylpropyl)amine,    -   bis(trimethoxysilylpropyl)amine,    -   gamma-(3,4-epoxycyclohexyl)propyltriethoxysilane,    -   gamma-(3,4-epoxycyclohexyl)propyltrimethoxysilane,    -   gamma-acryloxypropyltriethoxysilane,    -   gamma-acryloxypropyltrimethoxysilane,    -   gamma-aminopropyltriethoxysilane,    -   gamma-aminopropyltrimethoxysilane,    -   gamma-methacryloxypropyltriethoxysilane,    -   gamma-methacryloxypropyltrimethoxysilane,    -   gamma-ureidopropyltrialkoxysilane,    -   N-2-aminoethyl-3-aminopropyltriethoxysilane,    -   N-2-aminoethyl-3-aminopropyltrimethoxysilane,    -   N-2-aminomethyl-3-aminopropyltriethoxysilane,    -   N-2-aminomethyl-3-aminopropyltrimethoxysilane,    -   N-(3-(trimethoxysilyl)propyl)ethylenediamine,    -   N-beta-(aminoethyl)-gamma-aminopropyltriethoxysilane,    -   N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane,    -   N-(gamma-triethoxysilylpropyl)diethylenetriamine,    -   N-(gamma-trimethoxysilylpropyl)diethylenetriamine,    -   N-(gamma-triethoxysilylpropyl)dimethylenetriamine,    -   N-(gamma-trimethoxysilylpropyl)dimethylenetriamine,    -   poly(aminoalkyl)ethyldialkoxysilane,    -   poly(aminoalkyl)methyldialkoxysilane,    -   tris(3-(triethoxysilyl)propyl)isocyanurate,    -   tris(3-(trimethoxysilyl)propyl)isocyanurate,    -   ureidopropyltrialkoxysilane and    -   vinyltriacetoxysilane.

Optionally, in specific embodiments, the aqueous composition contains atleast one silane/silanol/siloxane/polysiloxane having afluorine-containing group. By choosing the silane compound(s) it is alsopossible to adjust the hydrophilicity/hydrophobicity according to thedesired objective.

Preferably, in some embodiments of the aqueous composition, at least oneat least partially hydrolysed, at least partially condensedsilane/silanol/siloxane/polysiloxane is added. In particular, whenmixing the aqueous composition, it is optionally possible to add atleast one already prehydrolysed, precondensedsilane/silanol/siloxane/polysiloxane. Such an addition is particularlypreferred.

In some embodiments, at least one at least extensively and/or completelyhydrolysed and/or at least extensively and/or completely condensedsilane/silanol/siloxane/polysiloxane can be added to the aqueouscomposition.

In many embodiments, a non-hydrolysed silane bonds to the metallicsurface less well than an at least partially hydrolysed silane/silanol.In many embodiments, an extensively hydrolysed and uncondensed or onlyslightly condensed silane/silanol/siloxane bonds to the metallic surfacemarkedly better than an at least partially hydrolysed and extensivelycondensed silane/silanol/siloxane/polysiloxane. In many embodiments, acompletely hydrolysed and extensively condensedsilanol/siloxane/polysiloxane exhibits only a slight tendency to becomechemically bonded to the metallic surface.

In some embodiments, at least one siloxane and/or polysiloxanecontaining little or no silanes/silanols—e.g. less than 20 or less than40 wt. % of the sum of silane/silanol/siloxane/polysiloxane—can be addedto the aqueous composition in addition and/or as an alternative tosilane(s)/silanol(s). The siloxane or polysiloxane is preferablyshort-chain and is preferably applied by means of a rollcoatertreatment. This then optionally affects the coating by strengthening thehydrophobicity and increasing the blank corrosion protection.

Preferably, the aqueous composition contains at least two or even atleast three titanium, hafnium, zirconium, aluminium and boron compounds,it being possible for these compounds to differ in their cations and/oranions. The aqueous composition, especially the bath composition,preferably contains at least one complex fluoride b) and particularlypreferably at least two complex fluorides selected from complexfluorides of titanium, hafnium, zirconium, aluminium and boron.Preferably, their difference lies not only in the type of complex. Theaqueous composition, especially the bath composition, preferably has acontent of compounds b), selected from titanium, hafnium, zirconium,aluminium and boron compounds, ranging from 0.01 to 50 g/l, calculatedas the sum of the corresponding metals. This content ranges particularlypreferably from 0.05 to 30 g/l, very particularly preferably from 0.08to 15 g/l and especially from 0.1 to 5 g/l.

Preferably, the composition contains at least one complex fluoride, thecontent of complex fluoride(s) ranging especially from 0.01 to 100 g/l,calculated as the sum of the corresponding metal complex fluorides asMeF₆. This content ranges preferably from 0.03 to 70 g/l, particularlypreferably from 0.06 to 40 g/l and very particularly preferably from 1to 10 g/l. The complex fluoride can be present especially as MeF₄ and/orMeF₆, but also in other states or intermediate states. Advantageously,at least one titanium complex fluoride and at least one zirconiumcomplex fluoride are simultaneously present in many embodiments. It canbe advantageous in many cases here to have at least one MeF₄ complex andat least one MeF₆ complex present in the composition simultaneously,especially a TiF₆ complex and a ZrF₄ complex. It can be advantageoushere to adjust these proportions of complex fluorides in the concentrateand transfer them to the bath in this way.

Surprisingly, the individual complex fluorides do not adversely affectone another when combined, but exhibit an unexpected positivereinforcing effect. These additions based on complex fluoride obviouslyact in a similar or identical manner. Surprisingly, if a combination ofcomplex fluorides based on titanium and zirconium was used rather than acomplex fluoride based only on titanium or only on zirconium, theresults obtained were always noticeably better than in the case of onlyone of these additions. A complex fluoride based on titanium orzirconium probably deposits on the surface as oxide and/or hydroxide.

It has now been established, surprisingly, that a good multimetaltreatment with a single aqueous composition is only possible if acomplex fluoride has been used, and that a very good multimetaltreatment with a single aqueous composition is only possible if at leasttwo different complex fluorides are used, e.g. those based on titaniumand zirconium. In a very wide variety of experiments, the complexfluorides used individually never gave results equivalent to those forthe combination of these two complex fluorides, independently of whatother additions were made.

As an alternative or in addition to at least one complex fluoride, it isalso possible to add another type of titanium, hafnium, zirconium,aluminium and/or boron compound, for example at least onehydroxycarbonate and/or at least one other water-soluble or sparinglywater-soluble compound, e.g. at least one nitrate and/or at least onecarboxylate.

It has now been shown, however, that an addition of silicon hexafluorideas the only complex fluoride added to an aqueous composition has adifferent and sometimes markedly poorer effect than the additions ofother complex fluorides.

Preferably, only types of cation, or corresponding compounds, from thegroup comprising magnesium, calcium, yttrium, lanthanum, cerium,vanadium, niobium, tantalum, molybdenum, tungsten, manganese, iron,cobalt, nickel, copper, silver and zinc, and particularly preferablyfrom the group comprising magnesium, calcium, yttrium, lanthanum,cerium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, copperand zinc, are selected as cations and/or corresponding compounds c),trace contents being excepted.

On the other hand, it has been shown, surprisingly, that iron and zinccations, and therefore also the presence in the bath of correspondingcompounds which can make an increased contribution, in the particularcase of acidic compositions, to dissolving such ions out of the metallicsurface, do not have an adverse effect, over wide ranges of contents, onthe bath behaviour, the layer formation or the layer properties.

Preferably, the aqueous composition, especially the bath composition,has a content of cations and/or corresponding compounds c) ranging from0.01 to 20 g/l, calculated as the sum of the metals. This content rangesparticularly preferably from 0.03 to 15 g/l, very particularlypreferably from 0.06 to 10 g/l and especially from 0.1 to 6 g/l.

The composition preferably contains at least one type of cation selectedfrom cations of cerium, chromium, iron, calcium, cobalt, copper,magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium,zinc, tin and other lanthanides, and/or at least one correspondingcompound. Preferably, not all the cations present in the aqueouscomposition have been not only dissolved out of the metallic surface bythe aqueous composition, but also at least partially or even extensivelyadded to the aqueous composition. A freshly prepared bath can thereforebe free of certain cations or compounds which are only freed or formedfrom reactions with metallic materials or from reactions in the bath.

Surprisingly, the addition of manganese ions or at least one manganesecompound has been shown to be particularly advantageous. Althoughapparently no manganese compound or almost no manganese compound isdeposited on the metallic surface, this addition clearly promotes thedeposition of silane/silanol/siloxane/polysiloxane, therebysignificantly improving the properties of the coating. Unexpectedly, anaddition of magnesium ions or at least one magnesium compound has alsobeen shown to be advantageous, since this addition promotes thedeposition of titanium and/or zirconium compounds, probably as oxideand/or hydroxide, on the metallic surface and thus markedly improves theproperties of the coating. A combined addition of magnesium andmanganese improves the coatings still further in some cases. Bycontrast, an addition of only 0.02 g/l of copper ions has not yet beenshown to have a significant influence. If the calcium ion content isincreased, care should be taken to ensure that a complex fluoride is notdestabilized by the formation of calcium fluoride.

Preferably, the composition has a content of at least one type of cationand/or corresponding compounds, selected from alkaline earth metal ions,ranging from 0.01 to 50 g/l, calculated as corresponding compounds,particularly preferably from 0.03 to 35 g/l, very particularlypreferably from 0.06 to 20 g/l and especially from 0.1 to 8 g/l. Thealkaline earth metal ions or corresponding compounds can help toreinforce the deposition of compounds based on titanium and/orzirconium, which is often advantageous especially for increasing thecorrosion resistance.

Preferably, the composition has a content of at least one type ofcation, selected from cations of iron, cobalt, magnesium, manganese,nickel, yttrium, zinc and lanthanides, and/or of at least onecorresponding compound c), ranging especially from 0.01 to 20 g/l,calculated as the sum of the metals. This content ranges particularlypreferably from 0.03 to 15 g/l, very particularly preferably from 0.06to 10 g/l and especially from 0.1 to 6 g/l.

Preferably, the composition contains at least one organic compound d)selected from monomers, oligomers, polymers, copolymers and blockcopolymers, especially at least one compound based on acrylic, epoxideand/or urethane. At least one organic compound having at least one silylgroup can also be used here, in addition or as an alternative. It ispreferred in some embodiments to use organic compounds having a contentor a higher content of OH groups, amine groups, carboxylate groups,isocyanate groups and/or isocyanurate groups.

Preferably, the composition has a content of at least one organiccompound d), selected from monomers, oligomers, polymers, copolymers andblock copolymers, ranging from 0.01 to 200 g/l, calculated as addedsolids. The content ranges particularly preferably from 0.03 to 120 g/l,very particularly preferably from 0.06 to 60 g/l and especially from 0.1to 20 g/l. In some embodiments, such organic compounds can help tohomogenize the formation of the coating. These compounds can contributeto the formation of a more compact, denser, more chemically resistantand/or more water-resistant coating, compared with coatings based onsilane/silanol/siloxane/polysiloxane etc. without these compounds. Thehydrophilicity/hydrophobicity can also be adjusted according to thedesired objective by the choice of organic compound(s). However, astrongly hydrophobic coating is problematic in some applications becauseof the required bonding of especially water-based lacquers, although astronger hydrophobicity can be established in the case of powdercoatings in particular. When using an addition of at least one organiccompound, a combination with compounds having a certain functionalitycan prove particularly advantageous, examples being compounds based onamines/diamines/polyamines/urea/imines/diimines/polyimines orderivatives thereof, compounds based in particular on cappedisocyanate/isocyanurate/melamine compounds, and compounds with carboxyland/or hydroxyl groups, e.g. carboxylates, longer-chain sugar-likecompounds, e.g. (synthetic) starch, cellulose, saccharides, long-chainalcohols and/or derivatives thereof. The long-chain alcohols added areespecially those having 4 to 20 C atoms, such as a butanediol, a butylglycol, a butyl diglycol, an ethylene glycol ether such as ethyleneglycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycolmonomethyl ether, ethyl glycol propyl ether, ethylene glycol hexylether, diethylene glycol methyl ether, diethylene glycol ethyl ether,diethylene glycol butyl ether or diethylene glycol hexyl ether, or apropylene glycol ether such as propylene glycol monomethyl ether,dipropylene glycol monomethyl ether, tripropylene glycol monomethylether, propylene glycol monobutyl ether, dipropylene glycol monobutylether, tripropylene glycol monobutyl ether, propylene glycol monopropylether, dipropylene glycol monopropyl ether, tripropylene glycolmonopropyl ether or propylene glycol phenyl ether, trimethylpentanedioldiisobutyrate, a polytetrahydrofuran, a polyetherpolyol and/or apolyesterpolyol.

The weight ratio of compounds based onsilane/silanol/siloxane/polysiloxane, calculated on the basis of thecorresponding silanols, to compounds based on organic polymers,calculated as added solids, in the composition, ranges preferably from1:0.05 to 1:30, particularly preferably from 1:0.1 to 1:2 and veryparticularly preferably from 1:0.2 to 1:20. In many embodiments thisratio ranges from 1:0.25 to 1:12, from 1:0.3 to 1:8 or from 1:0.35 to1:5.

It has now been found, surprisingly, that an addition of organic polymerand/or copolymer, in particular, markedly improves the corrosionresistance, especially on iron and steel, and is of particular advantagefor a higher process safety and constantly good coating properties.

The composition optionally has a content of silicon-free compoundshaving at least one amino, urea and/or ureido group, especiallyamine/diamine/polyamine/urea/imine/diimine/polyimine compounds andderivatives thereof, ranging preferably from 0.01 to 30 g/l, calculatedas the sum of the corresponding compounds. The content rangesparticularly preferably from 0.03 to 22 g/l, very particularlypreferably from 0.06 to 15 g/l and especially from 0.1 to 10 g/l. It ispreferable to add at least one compound such as aminoguanidine,monoethanolamine, triethanolamine and/or a branched urea derivative withan alkyl radical. An addition of aminoguanidine, for example, markedlyimproves the properties of the coatings according to the invention.

Optionally, the composition has a content of nitrite anions andcompounds with a nitro group preferably ranging from 0.01 to 10 g/l,calculated as the sum of the corresponding compounds. The content rangesparticularly preferably from 0.02 to 7.5 g/l, very particularlypreferably from 0.03 to 5 g/l and especially from 0.05 to 1 g/l. Thissubstance is preferably added as nitrous acid, HNO₂, an alkali-metalnitrite, ammonium nitrite, nitroguanidine and/orparanitrotoluenesulfonic acid, especially as sodium nitrite and/ornitroguanidine.

It has now been found, surprisingly, that an addition of nitroguanidine,in particular, to the aqueous composition makes the appearance of thecoatings according to the invention very homogeneous and perceptiblyincreases the coating quality. This has a very positive effectespecially on “sensitive” metallic surfaces such as sand-blasted iron orsteel surfaces. An addition of nitroguanidine noticeably improves theproperties of the coatings according to the invention. It has now beenfound, surprisingly, that an addition of nitrite can markedly reduce therusting tendency particularly of iron and steel surfaces.

Optionally, the composition has a content of compounds based onperoxide, e.g. hydrogen peroxide and/or at least one organic peroxide,preferably ranging from 0.005 to 5 g/l, calculated as H₂O₂. The contentranges particularly preferably from 0.006 to 3 g/l, very particularlypreferably from 0.008 to 2 g/l and especially from 0.01 to 1 g/l. Iftitanium is present, the bath often contains a titanium peroxo complexthat colours the solution or dispersion orange. Typically, however, thiscolouration is not in the coating because this complex is apparently notincorporated as such into the coating. The titanium or peroxide contentcan therefore be estimated via the color of the bath. The substance ispreferably added as hydrogen peroxide.

It has now been found, unexpectedly, that an addition of hydrogenperoxide to the aqueous composition according to the invention improvesthe optical quality of the coated substrates.

Optionally, the composition has a content of phosphorus-containingcompounds preferably ranging from 0.01 to 20 g/l, calculated as the sumof the phosphorus-containing compounds. These compounds preferablycontain phosphorus and oxygen, especially as oxyanions and correspondingcompounds. The content ranges particularly preferably from 0.05 to 18g/l, very particularly preferably from 0.1 to 15 g/l and especially from0.2 to 12 g/l. Preferably, at least one orthophosphate, at least oneoligomeric and/or polymeric phosphate and/or at least one phosphonateare added in each case as substance d₄). The at least one orthophosphateand/or salts thereof and/or esters thereof can be e.g. at least onealkali-metal phosphate, at least one orthophosphate containing iron,manganese and/or zinc, and/or at least one of their salts and/or esters.Instead or in addition, it is also possible to add in each case at leastone metaphosphate, polyphosphate, pyrophosphate, triphosphate and/orsalts thereof and/or esters thereof. As phosphonate it is possible toadd e.g. at least one phosphonic acid, such as at least onealkyldiphosphonic acid, and/or salts thereof and/or esters thereof. Thephosphorus-containing compounds of this group of substances are notsurfactants.

It has now been found, surprisingly, that an addition of orthophosphateto the aqueous composition according to the invention markedly improvesthe quality of the coatings, especially on electrogalvanized substrates.

It has now also been found, surprisingly, that an addition ofphosphonate to the aqueous composition according to the inventionnoticeably improves the corrosion resistance of aluminium-rich surfaces,especially as regards values in the CASS test.

Optionally, the aqueous composition contains at least one type of anionselected from carboxylates, e.g. acetate, butyrate, citrate, formate,fumarate, glycolate, hydroxyacetate, lactate, laurate, maleate,malonate, oxalate, propionate, stearate and tartrate, and/or at leastone corresponding undissociated and/or only partially dissociatedcompound.

Optionally, the composition has a content of carboxylate anions and/orcarboxylate compounds ranging from 0.01 to 30 g/l, calculated as the sumof the corresponding compounds. The content ranges particularlypreferably from 0.05 to 15 g/l, very particularly preferably from 0.1 to8 g/l and especially from 0.3 to 3 g/l. Particularly preferably, in eachcase at least one citrate, lactate, oxalate and/or tartrate can be addedas carboxylate. The addition of at least one carboxylate can help tocomplex a cation and keep it in solution more easily, thereby making itpossible to increase the stability and controllability of the bath.Surprisingly, it has been found that the bonding of a silane to themetallic surface can in some cases be facilitated and improved by acarboxylate content.

Preferably, the composition also contains nitrate. Preferably, itcontains a nitrate content in the range from 0.01 to 20 g/l, calculatedas the sum of the corresponding compounds. The content rangesparticularly preferably from 0.03 to 12 g/l, very particularlypreferably from 0.06 to 8 g/l and especially from 0.1 to 5 g/l. Nitratecan help to homogenize the formation of the coating, especially onsteel. Nitrite may be converted to nitrate, usually only partially.Nitrate can be added especially as an alkali-metal nitrate, ammoniumnitrate, a heavy metal nitrate, nitric acid and/or a correspondingorganic compound. The nitrate can markedly reduce the rusting tendency,especially on steel and iron surfaces. The nitrate can optionallycontribute to the formation of a defect-free coating and/or anexceptionally even coating that may be free of optically recognizablemarks.

The composition preferably contains at least one type of cation selectedfrom alkali-metal ions, ammonium ions and corresponding compounds,especially potassium and/or sodium ions, or at least one correspondingcompound.

Optionally, the composition has a free fluoride content ranging from0.001 to 3 g/l, calculated as F⁻. The content ranges preferably from0.01 to 1 g/l, particularly preferably from 0.02 to 0.5 g/l and veryparticularly preferably up to 0.1 g/l. It has been determined that it isadvantageous in many embodiments to have a low free fluoride content inthe bath because the bath can then be stabilized in many embodiments. Anexcessively high free fluoride content can sometimes adversely affectthe deposition rate of cations. In addition, undissociated and/oruncomplexed fluoride can also occur in many cases, especially in therange from 0.001 to 0.3 g/l. Such an addition is preferably made in theform of hydrofluoric acid and/or its salts.

Preferably, the composition has a content of at least onefluoride-containing compound and/or fluoride anions, calculated as F⁻and without including complex fluorides, especially at least onefluoride from alkali-metal fluoride(s), ammonium fluoride and/orhydrofluoric acid, ranging particularly preferably from 0.001 to 12 g/l,very particularly preferably from 0.005 to 8 g/l and especially from0.01 to 3 g/l. The fluoride ions or corresponding compounds can help tocontrol the deposition of the metal ions on the metallic surface sothat, for example, the deposition of the at least one zirconium compoundcan be increased or decreased as required. The weight ratio of the sumof the complex fluorides, calculated as the sum of the associatedmetals, to the sum of the free fluorides, calculated as F⁻, ispreferably greater than 1:1, particularly preferably greater than 3:1,very particularly preferably greater than 5:1 and especially greaterthan 10:1.

In the process according to the invention, the aqueous composition cancontain at least one compound selected from alkoxides, carbonates,chelates, surfactants and additives, e.g. biocides and/or defoamers.

Acetic acid, for example, can be added as a catalyst for the hydrolysisof a silane. The pH of the bath can be raised e.g. with ammonia/ammoniumhydroxide, an alkali-metal hydroxide and/or a compound based on amine,such as monoethanolamine, while the pH of the bath can preferably belowered with acetic acid, hydroxyacetic acid and/or nitric acid. Suchadditions belong to the substances that influence the pH.

The aforementioned contents or additions normally have a beneficialeffect in the aqueous compositions according to the invention in thatthey help to improve further the good properties of the aqueous basecomposition according to the invention consisting of components a) andb) and solvent(s). These additions normally act in the same way if onlyone titanium compound or only one zirconium compound, or a combinationthereof, is used. However, it has been shown, surprisingly, that thecombination of at least one titanium compound and at least one zirconiumcompound, especially as complex fluorides, significantly improves theproperties particularly of the coatings produced therewith.Surprisingly, the different additives thus function as in a modularsystem and make a substantial contribution to optimization of theparticular coating. In the specific case where a so-called multimetalmix is used, as often occurs in the pretreatment of car bodies and inthe treatment or pretreatment of different hardware or assembly parts,the aqueous composition according to the invention has proved verysuitable since the composition containing the various additives can bespecifically optimized to the particular multimetal mix and itspeculiarities and requirements.

With the process according to the invention, a mix of different metallicmaterials, e.g. as in the case of car bodies or different hardware, canbe coated with the aqueous coating in the same bath. Here, for example,any desired mix of substrates with metallic surfaces, selected from castiron, steel, aluminium, aluminium alloys, magnesium alloys, zinc andzinc alloys, can be coated simultaneously and/or successively accordingto the invention, it being possible for the substrates to be at leastpartially coated with metal and/or to consist at least partially of atleast one metallic material.

Provided at least one other component and/or traces of other substancesare not present, the remainder to 1000 g/l consists of water or of waterand at least one organic solvent such as ethanol, methanol, isopropanolor dimethylformamide (DMF). Preferably, in most embodiments, the organicsolvent content is particularly low or zero. Because of the hydrolysisof the at least one silane present, a content especially of at least onealcohol, e.g. ethanol and/or methanol, can appear. It is particularlypreferable not to add any organic solvent.

The composition is preferably free or substantially free of all types ofparticles, or particles with a mean diameter greater than 0.02 μm, whichmight be added e.g. in the form of oxides such as SiO₂.

Only if the coatings are dried e.g. for 5 minutes at 80° C. PMT (peakmetal temperature), for 25 minutes at 70° C. PMT or more substantiallyare these coatings normally insensitive to water, because thecondensation of the silanes/silanols/siloxanes/polysiloxanes is moreadvanced. The extent of drying, which is associated with condensationand makes the siloxane/polysiloxane-containing coating rinse-resistant,varies according to the existence of phases, the coating and the type ofrinsing.

The applied siloxane/polysiloxane-containing coating is preferablyfreshly applied and/or is optionally only slightly dried-on, if at all,when it is rinsed. The coating is preferably rinsed within 20 seconds ofapplication. As the silane-containing aqueous composition is at atemperature ranging preferably from 10 to 50° C., particularlypreferably from 15 to 35° C., when it is applied, and because the objectto be coated is also at a temperature ranging preferably from 10 to 50°C., particularly preferably from 15 to 35° C., these temperatures areusually not sufficiently high and usually not sufficiently different forrapid drying of the wet film to take place.

The fluid used for rinsing is preferably a liquid particle-free fluid,especially water or a solution. The fluid is particularly preferablywater of tap water grade, a pure grade of water such as demineralizedwater, or a grade of water containing e.g. at least one surfactantcapable of homogenizing the wet film. The fluid is at a temperatureranging preferably from 10 to 50° C., particularly preferably from 15 to35° C. It can wet the objects, coated with the wet film, by dipping in abath and/or in a liquid jet or film, by spraying, by atomization or by asimilar form of wetting in the liquid film and/or jet of a rinsing ring.Preferably, the liquid jet or film impinges on thesilane/silanol/siloxane/polysiloxane-containing coating with a pressurenot exceeding 2 bar.

The composition is preferably poor in, substantially free of or free oflarger contents or contents exceeding 1 g/l of water hardeners such ascalcium. The aqueous composition is preferably free of or poor in lead,cadmium, chromate, cobalt, nickel and/or other toxic heavy metals.Preferably, such substances are not deliberately added, although atleast one heavy metal, dissolved out of a metallic surface, can beentrained e.g. from another bath and/or can occur as an impurity. Thecomposition is preferably poor in, substantially free of or totally freeof bromide, chloride and iodide, since these can contribute to corrosionunder certain circumstances.

The layer thickness of the coatings produced according to the inventionranges preferably from 0.005 to 0.3 μm, particularly preferably from0.01 to 0.25 μm and very particularly preferably from 0.02 to 0.2 μm,and is frequently about 0.04 μm, about 0.06 μm, about 0.08 μm, about 0.1μm, about 0.12 μm, about 0.14 μm, about 0.16 μm or about 0.18 μm. Thecoatings containing organic monomer, oligomer, polymer, copolymer and/orblock copolymer are often somewhat thicker than those that are free oralmost free thereof.

Preferably, the composition forms a coating with a layer weight which,based only on the titanium and/or zirconium content, ranges from 1 to200 mg/m², calculated as elemental titanium. This layer weight rangesparticularly preferably from 5 to 150 mg/m² and very particularlypreferably from 8 to 120 mg/m² and, in particular, is about 10, about20, about 30, about 40, about 50, about 60, about 70, about 80, about90, about 100 or about 110 mg/m².

Preferably, the composition forms a coating with a layer weight which,based only on siloxanes/polysiloxanes, ranges from 0.2 to 1000 mg/m²,calculated as the corresponding extensively condensed polysiloxane. Thislayer weight ranges particularly preferably from 2 to 200 mg/m² and veryparticularly preferably from 5 to 150 mg/m² and, in particular, is about10, about 20, about 30, about 40, about 50, about 60, about 70, about80, about 90, about 100, about 110, about 120, about 130 or about 140mg/m².

As an alternative to the process sequence proposed hitherto, which alsoforms the basis of the process sequence in Table 1 below, it is possibleon the one hand, before the silane pretreatment according to theinvention, also to carry out a prerinsing step and/or a first silanecoating step with an aqueous composition containing at least one silane,at least one compound selected from fluoride-free compounds of titanium,hafnium, zirconium, aluminium and boron, at least one more highlydiluted alkali solution such as NaOH, and/or at least one complexfluoride, and/or on the other hand, after the silane pretreatmentaccording to the invention, to carry out at least one rinsing step withan aqueous composition containing not just water and optionallycontaining at least one surfactant to homogenize the wet film. It wasfound, however, that the properties of the coatings produced with such aprerinsing and/or afterrinsing step and with the silane pretreatmentaccording to the invention, if rinsed beforehand, always gavesignificantly inferior results for all the corrosion and lacqueradhesion values if the prerinsing step was carried out not just withwater or water containing highly diluted alkali solution and if theafterrinsing step involved more than water and at least one surfactant.

If necessary, the coating produced with the aqueous compositionaccording to the invention can then be coated with at least one primer,lacquer or adhesive and/or with a lacquer-like organic composition,optionally at least one of these other coatings being cured by heatingand/or irradiation.

The metallic substrates coated by the process according to the inventioncan be used in the automobile industry, for railway vehicles, in theaerospace industry, in apparatus engineering, in mechanical engineering,in the building industry, in the furniture industry, for the manufactureof crash barriers, lamps, profiles, sheathing or hardware, for themanufacture of car bodies or body parts, individual components orpreassembled/connected elements, preferably in the automobile oraeronautical industry, or for the manufacture of appliances orinstallations, especially household appliances, control devices, testingdevices or structural elements.

The existing plants for the cleaning and phosphatizing of car bodiesbefore lacquering often involve the following process stages shown inthe middle column of Table 1. The right column shows the process stageswhich have been recommended, surprisingly, in a shortened processsequence for the cleaning and silane coating of car bodies.

TABLE 1 Typical sequence of process stages for the phosphatizing of carbodies, or recommended sequence for the silane coating of car bodiesPhosphatizing Silane coating Alkaline cleaning 1 heated heated Alkalinecleaning 2 heated heated Rinsing 1 tap water tap water Rinsing 2 tapwater demin. water Activation very often, with (n/a) Ti or Zn phosphateRinsing 3 optional, if not (n/a) previously activated Pretreatmentphosphatizing, silane coating heated Rinsing 4 tap water demin. waterRinsing 5 demin. water demin. water Afterrinsing solution optional (n/a)Rinsing 6 demin. water (n/a) Rinsing ring optional (n/a)

It has also been shown, surprisingly, that it is not only possible touse certain solutions, based not just on silane, to produce coatingswhich, even without more substantial drying of the freshly appliedcoating, are not only sufficiently rinse-resistant to water, but alsohave somewhat better layer properties than comparable thoroughly driedcoatings. Apparently, the silane-based coatings that are not moresubstantially dried are more reactive than a lacquer or a lacquer-likecomposition, e.g. cathodic dip lacquer, and therefore exhibit anadequate adhesion. This makes it possible to dispense with the dryingstep hitherto regarded as necessary, and with the drying channel that ispossibly more than 10 metres long.

Given that the development of the zinc/manganese/nickel phosphatizing ofcar bodies has spanned several decades, the phosphate layers of thistype produced today are of extremely high quality. Nevertheless,contrary to expectation, it was possible to achieve the samehigh-quality properties with the silane-containing coatings.Surprisingly, the process according to the invention makes it possibleto carry out the pretreatment of car bodies with silane-based solutions,using relatively small contents of the aqueous compositions, withoutimpairing the quality of the coatings. If, however, markedly largercontents of the bath components are chosen, this increases the costs butthe quality of the coatings produced cannot usually be improved anyfurther.

The process according to the invention makes it possible to reduce thepretreatment step of 3 to 5 minutes in the phosphatizing process toapprox. 2 minutes in the silane-based coating process, and to dispensewith heating, as in the phosphatizing process, to temperatures oftenranging from 50 to 60° C. However, if the composition is lower, the bathis preferably heated to temperatures ranging from 15 to 25° C.

The process according to the invention makes it possible not only tocarry out the pretreatment of car bodies in shorter plants that areappreciably less expensive to operate, but also to work in a manner thatis considerably friendlier to the environment, because the amounts ofslurry containing heavy metal that has to be disposed of can beminimized, because water can be circulated under greater pressure andalso because the water throughput can be markedly reduced. This affordsa pronounced reduction both in the consumption of chemicals and in thetreatment costs because the amount of slurry obtained is less than 1% ofthat previously obtained from phosphatizing, based on the metallicsurface to be coated, so the cost of disposing of chemical waste isgreatly reduced.

An addition of manganese has surprisingly proved particularlyadvantageous: Although apparently no or almost no manganese compound isdeposited on the metallic surface, the addition greatly promotes thedeposition of silane/silanol/siloxane/polysiloxane on the metallicsurface. When adding nitroguanidine, it was found, surprisingly, thatthe optical characteristics of the coated metallic sheets are veryuniform, especially on sensitive surfaces such as sand-blasted iron orsteel surfaces. Unexpectedly, an addition of nitrite markedly reducedthe rusting tendency of steel substrates. It was found, surprisingly,that every addition mentioned in the present patent application ashaving a significantly positive effect has an additive effect onimproving the coating according to the invention: Choosing severaladditions, in a similar manner to a modular system, enables thedifferent properties, especially of a multimetal system, to be furtheroptimized.

It has now been found, surprisingly, that a good multimetal treatmentwith a single aqueous composition is only possible if a complex fluoridehas been used, and that a very good multimetal treatment with a singleaqueous composition is only possible if at least two different complexfluorides are used, e.g. those based on titanium and zirconium. In avery wide variety of experiments, the results obtained for complexfluorides used individually were never as good as those obtained for thecombination of these two complex fluorides, independently of what otheradditions were made.

The possibility of such a large increase in quality of aqueouscompositions containing silane/silanol/siloxane/polysiloxane could notbe anticipated. Surprisingly, however, a marked increase in the level ofquality in all tests was also found when using aqueous compositionsbased on a silane and only one titanium-based or zirconium-based complexfluoride.

It was further surprising that, when testing the lacquer adhesion, stonechip resistance scores of 1 or 2 were obtained, even on steel, when acomposition containing at least one silane and at least one complexfluoride was applied by the process according to the invention: Steelhas proved to be the most problematic material for aqueous compositionsbased on a silane and only one titanium-based or zirconium-based complexfluoride, especially in terms of the corrosion resistance (cf., forexample, E 5).

In the case of aluminium and aluminium alloys, experience shows that theCASS test is problematic, but this also turned out markedly better thanexpected with the compositions according to the invention.

EXAMPLES AND COMPARATIVE EXAMPLES

The Examples according to the invention (E) and Comparative Examples(CE) described below are intended to illustrate the subject matter ofthe invention in greater detail.

The aqueous bath compositions are prepared as mixtures according toTable 2 using already prehydrolysed silanes. They each containpredominantly one silane and optionally also have small contents of atleast one other similar silane, where here again the word silane is usedrather than silane/silanol/siloxane/polysiloxane by way ofsimplification, and where normally these various compounds, sometimes ina larger number of similar compounds, also pass through into theformation of the coating, so there are often several similar compoundspresent in the coating as well. Depending on the silane, theprehydrolysis step can also take several days at room temperature, withvigorous stirring, if the silanes to be used are not already present inprehydrolysed form. The prehydrolysis of the silane is carried out byplacing the silane in excess water and optionally catalysing with aceticacid. Acetic acid was added in only a few embodiments for the solepurpose of adjusting the pH. In some embodiments, acetic acid is alreadypresent as a hydrolysis catalyst. Ethanol is formed in the hydrolysis,but is not added. The finished mixture is used fresh.

Then, for each test, at least 3 sheets of cold-rolled steel (CRS),aluminium alloy Al6016, steel hot-dip galvanized or electrogalvanized onboth sides, or Galvaneal® (ZnFe layer on steel), previously cleaned withan aqueous alkaline cleaner and rinsed with industrial water and thenwith demineralized water, are brought into contact on both sides withthe appropriate treatment liquid at 25° C. by spraying, dipping orrollcoater treatment. Immediately thereafter, the sheets pretreated inthis way are briefly rinsed with demineralized water. The sheets of theComparative Examples are dried at 90° C. PMT and then lacquered with acathodic automobile dip lacquer (CDL). The sheets of the Examplesaccording to the invention, however, are rinsed immediately after thesilane pretreatment and dipped in the CDL bath immediately afterrinsing. These sheets were then provided with a complete commercialautomotive lacquer system (filler, covering lacquer, transparentlacquer; overall thickness of stacked layers, including CDL, approx. 105μm) and tested for their corrosion protection and lacquer adhesion. Thecompositions and properties of the treatment baths and the properties ofthe coatings are collated in Table 2.

The organofunctional silane A is an amino-functional trialkoxysilane andhas one amino group per molecule. Like all the silanes used here, it isin extensively or almost completely hydrolysed form in the aqueoussolution. The organofunctional silane B has one terminal amino group andone ureido group per molecule. The non-functional silane C is abis-trialkoxysilane; the corresponding hydrolysed molecule has up to 60Hgroups on two silicon atoms.

The complex fluorides of aluminium, silicon, titanium or zirconium areused extensively in the form of an MeF₆ complex, but the complexfluorides of boron are used extensively in the form of an MeF₄ complex.Manganese is added to the particular complex fluoride solution asmetallic manganese and dissolved therein. This solution is mixed withthe aqueous composition. If no complex fluoride is used, manganesenitrate is added. The silylated epoxy polymer has a low content of OH⁻and isocyanate groups, so it can also subsequently be chemicallycrosslinked at temperatures above 100° C.

The silanes present in the aqueous composition—concentrate and/orbath—are monomers, oligomers, polymers, copolymers and/or reactionproducts with other components due to hydrolysis reactions, condensationreactions and/or other reactions. The reactions take place especially inthe solution, during drying or optionally also during curing of thecoating, especially at temperatures above 70° C. All the concentratesand baths proved to be stable for one week without undergoing changes orprecipitations. No ethanol was added. Ethanol contents in thecompositions originate only from chemical reactions.

In the majority of Examples and Comparative Examples, the pH is adjustedwith ammonia if at least one complex fluoride is present and with anacid in other cases. All the baths have a good solution quality andalmost always a good stability. There are no precipitations in thebaths. In the Examples according to the invention and the ComparativeExamples, the coating pretreatment with the silane-containing solutionis immediately followed firstly by one brief rinse with demineralizedwater. The freshly applied wet film was not able to dry on moresubstantially because it was rinsed within 5 seconds of application ofthe silane-containing coating. Both the freshly coated substrate and therinsing water were at room temperature. A rinse was necessary to preventsubstances in the pretreatment solution from being introduced into thesubsequent lacquer bath. The freshly rinsed, coated substrate was thenimmediately dipped in the cathodic dip lacquer, so no further dryingcould occur. Whereas the coated sheets of the Examples according to theinvention were coated with a cathodic dip lacquer immediately afterrinsing, without intermediate drying, those of the Comparative Exampleswere dried in an oven for 5 minutes at 120° C. immediately afterrinsing.

Because of the interference colours, only the coatings on steel can besignificantly examined visually, allowing an assessment of thehomogeneity of the coating. The coatings without any complex fluoridecontent are very inhomogeneous. Surprisingly, a coating with titaniumcomplex fluoride and zirconium complex fluoride proved to be markedlymore homogeneous than when only one of these complex fluorides had beenapplied. An addition of nitroguanidine, nitrate or nitrite likewiseimproves the homogeneity of the coating. In some cases the layerthickness increases with the concentration of these substances.

TABLE 2 Bath compositions in g/l, based on solids contents or, in thecase of silanes, on the weight of the hydrolysed silanes; residualcontent: water and usually a very small amount of ethanol; process dataand properties of the coatings Example/CE CE 1 E 1 CE 2 E 2 CE 3 E 3 CE4 E 4 CE 5 E 5 Organofunct. silane A 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.20.2 H₂TiF₆ as Ti — — 0.2 0.2 — — 0.2 0.2 0.2 0.2 H₂ZrF₆ as Zr — — — —0.2 0.2 0.2 0.2 0.2 0.2 Mn — — — — — — — — 0.3 0.3 Silylated epoxypolymer — — — — — — — — — — pH 10.5 10.5 4 4 4 4 4 4 4 4 Layer weight,mg/m², of 10-20 10-20 20-50 20-50 20-50 20-50 20-50 20-50 20-60 20-60silanol and metal BMW cross-cut test: score Steel 4 3 5 5 3 2 2 1 1 0E-zinc on steel 3 3 4 3 4 3 1-2 1 1 0 Hot-dip zinc on steel 2 2 4 3 4 31 0 0 0 AI 6016 2 2 2 2 2 2 1 1 1 0 Galvaneal ® 1 1 1 1 2 1 1 0 1 0 10VDA cycles, mm disbonding Steel 8 6 7 5 4 3 3 2.5 2 1 E-zinc on steel 54 3 2.5 4 4 2 1 1 <1 Hot-dip zinc on steel 4 4 2.5 2 3.5 3 <1 <1 <1 <1Galvaneal ® 2 2 2 1 1.5 1.5 <1 0 <1 <1 Stone chip resistance after VDAstress: score Steel 5 5 4 4 4 3 2-3 1 1 1 E-zinc on steel 5 4 3 2 4 3 21 1 1 Hot-dip zinc on steel 5 4 3 2 4 3 1 0 1 0 Galvaneal ® 4 4 2 2 3 21-2 0 1 0 Salt spray test, 1008 h Steel 7 6 4 4 3.5 3 2 1.5 1.5 <1 CASStest, mm disbonding AI 6016 6 6 3.5 3 3.5 3 2.5 2.5 1.5 1 Example/CE CE6 E 6 CE 7 E 7 CE 8 E 8 CE 9 E 9 Organofunct. silane A 0.1 0.1 0.3 0.30.2 0.2 0.2 0.2 H₂TiF₆ as Ti 0.1 0.1 0.3 0.3 0.2 0.2 0.2 0.2 H₂ZrF₆ asZr 0.1 0.1 0.3 0.3 0.4 0.4 0.2 0.2 Mn — — — — 0.3 0.3 — — Silylatedepoxy polymer — — — — — — 1.0 1.0 pH 4 4 4 4 4 4 4 4 Layer weight,mg/m², of 10-40 10-40 30-80 30-80 30-80 30-80 50-100 50-100 silanol andmetal BMW cross-cut test: score Steel 2 1 1 1 1 0 1 1 E-zinc on steel 11 1 1 1 1 0 0 Hot-dip zinc on steel 1 0 0-1 0-1 0-1 0 0 0 AI 6016 2 1 11 1 0 1 1 Galvaneal ® 1 0 0 0 0 0 0 0 10 VDA cycles, mm disbonding Steel3.5 2 1.5 1.5 1.5 <1 2.5 2 E-zinc on steel 3 1.5 1.5 1 1 <1 1 <1 Hot-dipzinc on steel 1.5 1 1 1 1 <1 <1 <1 Galvaneal ® 1 1 <1 <1 <1 <1 0 0 Stonechip resistance after VDA stress: score Steel 2 2 2 1 1-2 1 1 0-1 E-zincon steel 2 1 1-2 0 1 0 1 0-1 Hot-dip zinc on steel 1 1 1 0 1 0 0 0Galvaneal ® 1 0-1 0 0 0 0 0 0 Salt spray test, 1008 h Steel 2.5 2 1.5 <11.5 <1 1 1 CASS test, mm disbonding AI 6016 2.5 2 1.5 1 1.5 1 1.5 1

When the different metallic surfaces which have been coated areconsidered as a whole, all the Examples show a significant improvementin comparison with the respective Comparative Example, the same bathcomposition being applied each time, in one case with subsequent drying(as Comparative Example, CE) and in the other case without subsequentdrying (as Example according to the invention, E).

It was surprising that this improvement, which brings only a limitedimprovement to already good coating results, is systematically improvedby not drying after application of the aqueous composition. It istherefore possible, surprisingly, to achieve, by not drying, asignificant improvement which is universally almost independent of thechemical composition of the aqueous bath. It was further surprising thatthis improvement occurred both in the case of the solutions containingonly silane, and in the case of the solutions containing silane andcomplex fluoride and optionally also manganese ions. It is thereforeassumed that a similar constant improvement from drying to not dryingalso occurs in the case of solutions of similar composition or in thecase of solutions containing several different substances, based onsilane or on silane and complex fluoride. The greater the number ofdifferent substances present and the larger their inherently smallcontents, the better the corrosion resistance and lacquer adhesion canbe, provided any optimum is not exceeded.

The layer weight varies not only with the contents of the individualconstituents of the aqueous solutions, but also with the particular typeof metallic surface being coated. Choosing the bath components and theircontents makes it possible overall to achieve a very marked improvementin the corrosion resistance and lacquer adhesion.

Over the short period of use, all the bath compositions are found to bestable and satisfactory to apply. There are no differences in behaviour,visual impression or test results between the different Examples andComparative Examples which can be attributed to the treatmentconditions, e.g. application by spraying, dipping or rollcoatertreatment. The films formed are transparent and almost all areextensively homogeneous. They do not colour the coating. The filmsformed are transparent and almost all are extensively homogeneous. Thestructure, gloss and colour of the metallic surface appear to be onlyslightly changed by the coating. If a titanium and/or zirconium complexfluoride is present, iridescent layers are formed, especially on steelsurfaces. Combining several silanes has not so far brought about asignificant improvement in the corrosion protection, but this cannot beruled out. Furthermore, a content of H₃AlF₆ was found on aluminium-richmetallic surfaces due to corresponding reactions in the aqueouscomposition. Surprisingly, however, combining two or three complexfluorides in the aqueous composition has proved extremely beneficial.

The layer thickness of the coatings produced in this way—also dependenton the type of application, which was initially varied in specificexperiments—ranged from 0.01 to 0.16 μm and usually from 0.02 to 0.12 μmand was often up to 0.08 μm, being markedly greater when organic polymerwas added.

Given that the development of the zinc/manganese/nickel phosphatizing ofcar bodies has spanned several decades, the phosphate layers of thistype produced today are of extremely high quality. Nevertheless,contrary to expectation, it was possible to achieve the samehigh-quality properties with silane-containing coatings by means ofaqueous silane-containing compositions that have only been in use for afew years, even though a greater effort was required.

The corrosion protection scores in the cross-cut test according to DINEN ISO 2409, after storage for 40 hours in 5% NaCl solution according toBMW specification GS 90011, range from 0 to 5, 0 representing the bestvalues. In the salt spray/condensation water alternation test over 10cycles according to VDA test sheet 621-415 with alternating corrosionstress between salt spray test, perspiration water test and dryinginterval, the disbanding is measured on one side from the scratchoutwards and reported in mm, the disbanding ideally being as small aspossible. In the stone chip resistance test according to DIN 55996-1,the coated metallic sheets are bombarded with scrap steel after theaforementioned VDA alternation test over 10 cycles: The damage pictureis characterized by scores from 0 to 5, 0 representing the best results.In the salt spray test according to DIN 50021 SS, the coated sheets areexposed for up to 1008 hours to an atomized corrosive sodium chloridesolution; the disbanding is then measured in mm from the scratchoutwards, the scratch being made with a standard gouge down to themetallic surface, and the disbanding ideally being as small as possible.In the CASS test according to DIN 50021 CASS, the coated sheets made ofan aluminium alloy are exposed for 504 hours to an atomized specialcorrosive atmosphere; the disbanding is then measured in mm from thescratch outwards and ideally is as small as possible.

Other experiments on car body elements have shown that theelectrochemical conditions of the CDL bath may be very slightlyadaptable to the different kind of coating, but otherwise that theoutstanding properties obtained in laboratory experiments can bereproduced on car body elements.

1. A process comprising the steps of contacting a metallic surface witha first coating composition to form a first coating on the metallicsurface, wherein the first coating composition consists of: water; andat least one compound a) selected from the group consisting of a silane,a silanol, a siloxane and a polysiloxane, wherein the at least onecompound is capable of condensation; and rinsing the first coating withan aqueous surfactant-containing fluid without drying so that the atleast one compound a) does not condense before the rinsing step.
 2. Theprocess of claim 1, further comprising applying a second coating on thefirst coating.
 3. The process according to claim 2, comprising rinsingthe first coating with a fluid before applying the second coating. 4.The process according to claim 3, wherein the second coating is aconversion coating, a coating resulting from the application of anafter-rinsing solution, a coating based on a lacquer, a primer or anadhesive.
 5. The process according to claim 2, wherein the secondcoating is a conversion coating, a coating resulting from theapplication of an after-rinsing solution, a coating based on a lacquer,a primer or an adhesive.
 6. The process according to claim 1, whereinthe pH of the first coating composition is greater than 1.5 and lessthan
 9. 7. The process according to claim 1, wherein compound a) ispresent in an amount of from 0.005 to 80 g/l, calculated on the basis ofa corresponding silanol.
 8. The process according to claim 1, whereincompound a) contains at least one member selected from the groupconsisting of an amino group, an urea group and an ureido group.
 9. Theprocess of claim 1, wherein the aqueous surfactant-containing fluidcontains demineralized water.
 10. A process comprising the steps ofcontacting a metallic surface with a first coating composition to form afirst coating on the metallic surface, wherein the first coatingcomposition consists of: water; at least one compound a) selected fromthe group consisting of a silane, a silanol, siloxane and apolysiloxane, wherein the at least one compound is capable ofcondensation; and at least one compound b) selected from the groupconsisting of titanium, hafnium, zirconium, aluminum and boron; andrinsing the first coating with an aqueous surfactant-containing fluidwithout drying so that the at least one compound a) does not condensehefbre the rinsing step.
 11. The process of claim 10, further comprisingapplying a second coating on the first coating.
 12. The processaccording to claim 11, comprising rinsing the first coating with a fluidbefore applying the second coating.
 13. The process according to claim12, wherein the second coating is a conversion coating, a coatingresulting from the application of an after-rinsing solution, a coatingbased on a lacquer, a primer or an adhesive.
 14. The process accordingto claim 11, wherein the second coating is a conversion coating, acoating resulting from the application of an after-rinsing solution, acoating based on a lacquer, a primer or an adhesive.
 15. The processaccording to claim 10, wherein the pH of the first coating compositionis greater than 1.5 and less than
 9. 16. The process according to claim10, wherein compound a) is present in an amount of from 0.005 to 80 g/l,calculated on the basis of a corresponding silanol.
 17. The processaccording to claim 10, wherein compound a) contains at least one memberselected from the group consisting of an amino group, an urea group andan ureido group.
 18. The process of claim 10, wherein the aqueoussurfactant-containing fluid contains demineralized water.
 19. A processcomprising the steps of contacting a metallic surface with a firstcoating composition to form a first coating on the metallic surface,wherein the first coating composition consists of: water; at least onecompound a) selected from the group consisting of a silane, a silanol,a. siloxane and a polysiloxane, wherein the at least one compound iscapable of condensation; and at least one cation c) selected from acation of a metal of subgroup 1 to 3 and 5 to 8, including a lanthanide,and of main group 2 of the periodic table of the elements; and rinsingthe first coating with an aqueous surfactant-containing fluid withoutdrying so that the at least one compound a) does not condense hefbre therinsing step.
 20. The process of claim l9, further comprising applying asecond coating on the first coating.
 21. The process according to claim20, comprising rinsing the first coating with a fluid before applyingthe second coating.
 22. The process according to claim 21, wherein thesecond coating is a conversion coating, a coating resulting from theapplication of an after-rinsing solution, a coating based on a lacquer,a primer or an adhesive.
 23. The process according to claim 20, whereinthe second coating is a conversion coating, a coating resulting from theapplication of an after-rinsing solution, a coating based on a lacquer,a primer or an adhesive.
 24. The process according to claim 19, whereinthe pH of the first coating composition is greater than 1.5 and lessthan
 9. 25. The process according to claim 19, wherein compound a) ispresent in an amount of from 0.005 to 80 g/l, calculated on the basis ofa corresponding silanol.
 26. The process according to claim 19, whereincompound a) contains at least one member selected from the groupconsisting of an amino group, an urea group and an ureido group.
 27. Theprocess of claim 19, wherein the at least one compound c) is selectedfrom the group consisting of cerium, chromium, iron, calcium, cobalt,copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum,yttrium and zinc.
 28. The process of claim 19, wherein the aqueoussurfactant-containing fluid contains demineralized water.
 29. A. processcomprising the steps of contacting a metallic surface with a firstcoating composition to form a first coating on the metallic surface,wherein the first coating composition consists of: water; at least onecompound a) selected from the group consisting of a silane, a silanol, asiloxane and a polysiloxane, wherein the at least one compound iscapable of condensation; at least one compound b) selected from thegroup consisting of titanium, hafnium, zirconium, aluminum and boron;and at least one cation c) selected from a cation of a metal of subgroup1 to 3 and 5 to 8, including a lanthanide, and of main group 2 of theperiodic table of the elements; and rinsing the first coating with anaqueous surfactant-containing fluid without drying so that the at leastone compound a) does not condense before the rinsing step.
 30. Theprocess of claim 29, further comprising applying a second coating on thefirst coating.
 31. The process according to claim 30, comprising rinsingthe first coating with a fluid before applying the second coating. 32.The process according to claim 31, wherein the second coating is aconversion coating, a coating resulting from the application of anafter-rinsing solution, a coating based on a lacquer, a primer or anadhesive.
 33. The process according to claim 30, wherein the secondcoating is a conversion coating, a coating resulting from theapplication of an after-rinsing solution, a coating based on a lacquer,a primer or an adhesive.
 34. The process according to claim 29, whereinthe pH of the first coating composition is greater than 1.5 and lessthan
 9. 35. The process according to claim 29, wherein compound a) ispresent in an amount of from 0.005 to 80 gil, calculated on the basis ofa corresponding silanol.
 36. The process according to claim 29, whereincompound a) contains at least one member selected from the groupconsisting of an amino group, an urea group and an ureido group.
 37. Theprocess of claim 29, wherein the at least one compound c) is selectedfrom the group consisting of cerium, chromium, iron, calcium, cobalt,copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum,yttrium and zinc.
 38. The process of claim 29, wherein the aqueoussurfactant-containing fluid contains demineralized water.